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902 NKX019, an off-the-shelf CD19 CAR-NK cell, mediates improved anti-tumor activity and persistence in combination with CD20-directed therapeutic mAbs
  1. Mira Tohmé,
  2. Tina Davis,
  3. Max Zhang,
  4. Hadia Lemar,
  5. Bao Duong,
  6. Joanne Tan and
  7. James Trager
  1. Nkarta Therapeutics, South San Francisco, CA, United States


Background NKX019 is an investigational CD19-targeting chimeric antigen receptor (CAR) natural killer (NK) cell therapy with engineered persistence for treating B cell malignancies. NKX019 exhibits more rapid cytotoxic kinetics than CD19-directed CAR T cells, and lower production of cytokines associated with cytokine release syndrome (CRS).1 The safety and clinical activity of NKX019 are currently being evaluated in a phase I [GM1] clinical study [NCT05020678]. Recent studies2,3 have shown that combining NK cell therapies with monoclonal antibodies (mAbs) may improve targeted NK cell activation and overcome some of the disadvantages associated with the stand-alone use of therapeutic mAbs. CD20-targeted mAbs such as rituximab (RTX) and obinutuzumab (OBI), can mediate antibody-dependent cellular cytotoxicity (ADCC), a key effector mechanism of NK cells. RTX also activates some levels of caspase-dependent direct cell death (DCD). OBI is engineered to induce improved DCD and ADCC mechanisms.4 Antigen escape is reported in 30–95% of relapses after CD19-directed CAR T cell therapy in B cell –acute lymphoblastic leukemia (B-ALL).5 Here, we describe the potential advantage of using NKX019 in combination with [GM2] RTX or OBI to reduce relapse following monotherapy with either agent alone by targeting both CD19+and CD20+ malignant B cells.

Methods NK cells, isolated from healthy PBMCs, were expanded and engineered to express a CD19-targeted CAR and membrane-bound interleukin 15 to generate NKX019. NKX019 cells were cryopreserved and freshly thawed for experimental use.NKX019 mediated-cytotoxicity was assessed in both 4-Hour (4H) and extended assays in the presence or absence of anti-CD20 mAbs, RTX or OBI, using CD19+ and CD20+ expressing tumor B cell lines: Raji (lymphoblast-like), DOHH-2 (follicular lymphoma) and EHEB (B-Lymphoblastoid) cells. A non-glycosylated version of RTX (RTX mutant) with compromised ADCC function was used to evaluate ADCC-mediated vs ADCC-independent activity of NKX019.

Results NKX019 in combination with RTX or OBI demonstrated increased activity and persistence against tumor B cell lines in a 4H kill assay and in tumor rechallenge experiments. NKX019 in combination with RTX demonstrated an enhanced cytotoxicity against EHEB lymphoblastoid cell line in a manner consistent with ADCC. OBI demonstrated increased activity in comparison to RTX, as a single agent and in combination with NKX019 cells.

Conclusions This study demonstrates increased activity and persistence of NKX019 when used in combination with approved CD20-targeted mAbs, RTX and OBI, against B cell malignancies. A first-in -human Phase I clinical trial of NKX019 in combination with RTX is planned.


  1. Morisot N, Wadsworth S, Davis T, et al. 127 Preclinical evaluation of NKX019, a CD19-targeting CAR NK cell. J ImmunoTherapy Cancer. 2020;8(suppl 3):A78.

  2. Goodridge J, Mahmood S, Zhu H, et al. FT596: translation of first-of-kind multi-antigen targeted off-the-shelf CAR-NK cell with engineered persistence for the treatment of B cell malignancies. Blood. 2019;134(suppl 1):301.

  3. Cichocki F, Bjordahl R, Gaidarova S, et al. iPSC-derived NK cells maintain high cytotoxicity and enhance in vivo tumor control in concert with T cells and anti-PD-1 therapy. Sci Transl Med. 2020;12(568):eaaz5618.

  4. Luo C, Wu G, Huang X, et al. Efficacy and safety of new anti-CD20 monoclonal antibodies versus rituximab for induction therapy of CD20+B-cell non-Hodgkin lymphomas: a systematic review and meta-analysis. Sci Rep. 2021;11(1):3255.

  5. Spiegel JY, Patel S, Muffly L, et al. CAR T cells with dual targeting of CD19 and CD22 in adult patients with recurrent or refractory B cell malignancies: a phase 1 trial. Nat Med. 2021;27(8):1419–1431.

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